Grounding lugs for conduit fittings and the like



Jan. 23, 1968 F. L. BROWNE 3,365,693

GROUNDING LUGS FOR CONDUIT FITTINGS AND THE LIKE Filed Nov. 29, 1965 INVENTOR FEHNK L. BFZOWNE,

United States Patent 3,355,693 GROUNDING LUGS FOR CONDUKT GS AND THE LiKE Frank L. Browne, Wantagh, N.Y., assignor to (LZ. Electrical Manufacturing (10., Inc., New York,

N.Y., a corporation of New York Filed Nov. 29, 1965, Ser. No. 51%,316 1 Claim. (Cl. 339-14) ABSTRACT OF THE DISCLOSURE A grounding lug attached under tension to the end fitting of electrical steel conduit in the form of a block of conducting material of parallelepiped shape, with front and back, top and bottom and end walls; the front wall having an entrance slot for a ground wire across the upper front portion of the same and extending downward at the back into a substantially circular wire seating groove in the bottom portion of the block, a binding screw ex tending down through the top of the block over the wire seating groove; an opening from the wire seating groove through the back of the block, the back face of the block being concaved vertically on a curvature to fit the smallest end fitting with which the lug is to be used, and a mounting screw extending from the grooved portion through said opening in the back wall into a screw seat provided in the end fitting so that the mounting screw will tension the concaved back face of the lug against the curved surface of the conduit fitting and the pressure of the binding screw on the inserted grounding wire will exert an arching effect on the lug to apply greater holding tension on the mounting screw and force the lug into more intimate contact engagement with the end fitting.

The invention herein disclosed relates to grounding devices, particularly for the end fittings, bushings, insulated bushings and like parts used on electrical conduit.

Special objects of the invention are to provide a substantial rugged form of grounding lug readily attachable to the fitting or other part with which it is to be combined and to which grounding wires of different size and character, such as stranded or solid wire, insulated or noninsulated, may be readily secured and held, as through or end connections.

Further special objects of the invention are to provide such a grounding lug which may be used equally well on different size conduit fittings and which with these and other advantages may be produced at reasonable cost.

The foregoing and other desirable objects have been accomplished by novel features of construction, combination and relation of parts, as illustrated in the accompanying drawing and described in detail in the specification following.

The drawing accompanying and forming part of the specification is illustrative of a present preferred embodiment of the invention. Structure, however, may be moditied and changed as regards the immediate illustration; all within the true intent and scope of the invention, as hereinafter defined and claimed.

FIG. 1 in the drawing is a plan view of one of the ground lugs applied to an insulated bushing and holding a through grounding wire.

FIG. 2 is an enlarged cross sectional view on substantially the plane of line 2-2 of FIG. 1.

PEG. 3 is a broken front elevation of the lug in place on the insulated bushing.

The insulated bushing shown is of typical construction involving a metal ring 5, internally screw threaded to go over the end of electrical steel conduit and having a ring 6 of insulating material molded and interlocked therein at 7.

The body of the grounding lug is shown in the form of a solid block 8, usually of steel and in the shape of a parallelepiped having front and back faces, 9 and Ill, top and bottom 11 and 12, and side or end faces 13, 14.

The back face 10 is finished on a concavity 15, extending from top to bottom and on a radius substantially corresponding to the curvature of the smallest fitting or part to which the lug is to be applied, to closely fit the same and to provide ledges 16 at opposite side edges to firmly grip on parts of larger radius and to dig in to hold the block against turning under pressure of the securing screw.

An opening 17 is provided through the back wall of the block for securing screw 18, to engage in a corresponding screw seat 19, provided in the fitting or other part.

A slot 20 extends across the upper portion of the front or face, the full length of the block, of a width to pass the largest ground wire for which the device is intended and this slot is continued downward at the back into a seat 21 at the bottom, for the wire.

The front wall of this wire seating groove, providing the lower edge of the slot 20, is shown at 22, as extended above the center of the wire seating groove so as to hold the wire or strands of the wire against escape or spreading action.

The ground wire is clamped and held in place in its circular seat by a screw 23, entered through a screw passage 24, in the top of the lug directly over the wire seat or passage.

This clamping screw is shown as having a flat end 28 to grip the wire without spreading the strands or forcing the wire out of its seat.

It will be noted in FIG. 2 that the pressure applied by this screw, in clamping the wire tends to spread the separated top and bottom portions of the block, exerting a force to arch the back Wall of the block, thus to put extra pull or tension on the mounting screw 18, which makes the connection of the lug with the fitting all the more secure.

This assures firm and positive contact engagement of the grounding lug with the fitting or other part to which it is applied.

To facilitate the connection of the lug with the conduit fitting or other part, the front wall of the block is shown cut down or recessed at 25 in line with the head of the mounting screw 18, for admission of a screw driver or other tool.

The ground wire when in place covers the mounting screw and protects it against unauthorized tampering.

The wire opening extending as it does across the front of the lug and through from one side or end to the other, enables a grounding wire to be entered from the front or from either side and thus to admit a through connection or an end connection from either side and these connections easily to be made with conduits closely adjoining or under other more or less crowded conditions.

Another important point is that the clamp screw is located in the top of the block where it will be fully accessible to conduit installations; particularly important where the conduits are located close together or close to adjoining structures.

While particularly designed for conduit fittings, such as end bushings and the like, it will be appreciated that the invention may be used to advantage with other electrical devices, such as cable supports and the like.

FIG. 1 shows how a through connection may be made with insulation covered grounding wire 26, by simply removing enough insulation at 2 7 for entry of the bared portion of the wire sidewise through the slot in the front of the lug.

3 What is claimed is: 1. A self-tensioned grounding lug construction comprising the combination of a conducting ring member end fitting for electrical steel conduit,

said member having a screw seat in the side of the same,

a grounding lug of conducting material in the general form of a parallelepiped having front and back, top and bottom and end walls,

the front wall of said block having an entrance slot across the upper front portion of the same extending at the back down into a substantially circular wire seating groove in the bottom portion of the block,

a screw seat extending down through the top of the block over said wire seating groove,

an opening for a mounting screw extending from said groove out through the back of the block in line with said screw seat in the end fitting,

the back face of the block being concaved vertically from top to bottom on a curvature placing the opposite edges of the grooved portion in intimate contact with the curved surface of the end fitting,

a mounting screw extending from the wire seating groove through said opening in the back wall into said screw seat in the end fitting and tensioning the concaved wall in intimate contact with the end fitting, and

a binding screw extending down through said screw seat for clamping engagement with a grounding wire seated in said groove and applying an arching pressure on the block and exerting greater holding tension on the mounting screw.

References Cited UNITED STATES PATENTS 265,746 10/ 1882 Brewtnall 339-272 X 1,590,590 6/1926 Seymour et 211. 1,645,541 10/1927 Ogle 339-272 X 1,932,510 10/1933 Caruse. 2,710,381 6/1955 Morison. 3,066,277 11/1962 Edmunds.

3,076,952 2/1963 Powell 339272 X FOREIGN PATENTS 710,400 9/ 1941 Germany.

MARVIN A. CHAMPION, Primary Examiner. PATRICK A. CLIFFORD, Examiner. 

